Rubie's Official DC Comics Dawn of Justice Wonder Woman Ladies Costume, Adult Superhero Fancy Dress

I have just received this costume, but there is no where for the belt to attach at the back, does anyone know how to attach it ?

I have prime and really need a xs by friday could this’s possible please

Is this one piece or is it a skirt and top?

I’m a size 18-20 what size would you recommend. Is large big enough?